Understanding the nature and degree of hydraulic fracture complexity may be useful to the economic development of unconventional resources. Examples of hydraulic fracture techniques are described in the following papers: Mayerhofer et al., Integrating of Microseismic Fracture Mapping Results with Numerical Fracture Network Production Modeling in the Barnett Shale, Society of Petroleum Engineers (SPE) 102103, presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Tex., 24-24 Sep. 2006; Mayerhofer et al., What is Stimulated Reservoir Volume (SRV)?, SPE 119890 presented at the SPE Shale Gas Production Conference, Fort Worth, Tex., 16-18 Nov. 2008; Warpinski et al., Stimulating Unconventional Reservoirs: Maximizing Network Growth while Optimizing Fracture Conductivity, SPE 114173 presented at the SPE Unconventional Reservoirs Conference, Keystone, Colo., 10-12 Feb. 2008; and Cipolla et al., The Relationship between Fracture Complexity, Reservoir Properties, and Fracture Treatment Design, SPE 115769 presented at the SPE Annual Technical Conference and Exhibition, Denver, Colo., 21-24 Sep. 2008.
Complex hydraulic fracture propagation may be interpreted from microseismic measurements, for example, from unconventional reservoirs and tight gas reservoirs. Examples of complex hydraulic fracture techniques are provided in the following articles Maxwell et al., Microseismic Imaging of Hydraulic Fracture Complexity in the Barnett Shale, SPE 77440 presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Tex., Sep. 29-Oct. 2, 2002; Fisher et al., Integrating Fracture Mapping Technologies to Optimize Stimulations in the Barnett Shale, 77411 presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Tex., Sep. 29-Oct. 2, 2002; Cipolla et al., Effect of Well Placement on Production and Frac Design in a Mature Tight Gas Field, 95337 presented at the SPE Annual Technical Conference and Exhibition, Dallas, Tex., 9-12 Oct. 2005; and Warpinski et al., Stimulating Unconventional Reservoirs: Maximizing Network Growth while Optimizing Fracture Conductivity, SPE 114173 presented at the SPE Unconventional Reservoirs Conference, Keystone, Colo., 10-12 Feb. 2008.
In some cases, challenges may exist in distinguishing between small scale fracture complexity and simple planar fracture growth. A factor that may influence the creation of complex fracture systems is the presence and distribution of natural fractures. An example of complex fractures is shown in Cipolla et al., Integrating Microseismic Mapping and Complex Fracture Modeling to Characterize Fracture Complexity, SPE 140185 presented at the SPE Hydraulic Fracturing Technology Conference, The Woodlands, Tex., 24-26 Feb. 2011. Discrete Fracture Network (DFN) models have been used to simulate production in naturally fractured reservoirs as shown, for example, in the following papers: Dershowitz et al., A Workflow for Integrated Barnett Shale Reservoir Modeling and Simulation, SPE 122934 presented at the SPE Latin American and Caribbean Petroleum Engineering Conference, Cartagena, Columbia, 31 May-3 Jun. 2009; Qui et al., Applying Curvature and Fracture Analysis to the Placement of Horizontal Wells: Example from the Mabee (San Adres) Reservoir, Tex., SPE 70010 presented at the SPE Permian Basin Oil and Gas Recovery Conference, Midland, Tex. 15-17 May 2001; and Will et al., Integration of Seismic Anisotropy and Reservoir-Performance Data for Characterization of Naturally Fractured Reservoirs Using Discrete-Feature-Network Models, SPE 84412 presented at the SPE Annual Technical Conference and Exhibition, Denver, Colo., 5-8 Oct. 2003. These methods, along with log-based approaches (see, e.g., Bratton et al., Rock Strength Parameters from Annular Pressure While Drilling and Dipole Sonic Dispersion Analysis, Presented at the SPWLA 45th Annual Logging Symposium, Noordwijk, The Netherlands, 6-9 Jun. 2004) may be primarily descriptive. Some such methods may be used to characterize a structure of the natural fracture network by using seismic information to extend observations at the wellbore across the reservoir.
Some models have also been developed to quantify the propagation of complex hydraulic fracture networks in, for example, formations embedded with predefined, deterministic or stochastic natural fractures. Examples of complex fracture models are described in the following: Sahimi, M., New Models For Natural And Hydraulic Fracturing On Heterogeneous Rock, SPE 29648 presented at the SPE Western Regional Meeting, Bakersfield, Calif. (1995); Fomin et al., Advances In Mathematical Modeling Of Hydraulic Stimulation Of A Subterranean Fractured Reservoir, Proc. SPIE 5831: 148-154 (2005); Napier et al., Comparison Of Numerical And Physical Models For Understanding Shear Fracture Process, Pure Appl. Geophys, 163: 1153-1174 (2006); Tezuka et al., Fractured Reservoir Characterization Incorporating Microseismic Monitoring And Pressure Analysis During Massive Hydraulic Injection, IPTC 12391 presented at the International Petroleum Technology Conference, Kuala Lumpur, Malaysia (2008); Olsen et al., Modeling Simultaneous Growth Of Multiple Hydraulic Fractures And Their Interaction With Natural Fractures, SPE 119739 presented at the Hydraulic Fracturing Technology Conference, The Woodlands, Tex. (2009); and Xu et al., Characterization of Hydraulically Induced Shale Fracture Network Using an Analytical/Semi-Analytical Model, SPE 124697 presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 4-7 Oct. 2009; and Weng et al., Modeling of Hydraulic Fracture Propagation in a Naturally Fractured Formation, SPE 140253 presented at the SPE Hydraulic Fracturing Technology Conference, Woodlands, Tex., USA, 24-26 Jan. 2011. In some models, microseismic activity may be used to constrain the fracturing process.
Despite the advancements in fracture technology, it may be useful to have advanced techniques for extracting and/or assessing the complex fracture network.